Conventionally, there has been a dispensing method in which a suction quantity is detected and evaluated by suctioning liquid from a container into a pipette tip with a dispensing apparatus (Patent Document 1). In this dispensing method,
(a) when the lower end of a measuring instrument is immersed into liquid to be suctioned by a relative vertical movement between the measuring instrument and a container accommodating the liquid to be suctioned, suction of the liquid is commenced at a point where the pressure fluctuation range after the immersion is at a predetermined value with respect to the inner pressure of the measuring instrument before the lower end of the measuring instrument comes in contact with the liquid to be suctioned, and(b) after a predetermined period of time has elapsed, the lower end of the measuring instrument is separated from the liquid to be suctioned, and at this point it is determined whether or not it is a normal dispensed quantity based on the inner pressure of the measuring instrument.
In addition, there has been a method of pipetting a sample in which a liquid sample is suctioned and the suction state is evaluated, by means of the following method (Patent Document 2).
(a) The pressure inside a pipetter is measured in the initial state, and this value is taken as a reference pressure reading value.
(b) Then while lowering the pipetter towards the liquid sample within a container, the pressure inside the pipetter is made negative to thereby suction air,
(c) and in the case of monitoring pressure change within the pipetter, when a rapid pressure change is seen, this is considered to be when the distal end of the pipette tip reaches the liquid surface. Therefore it is considered that the liquid surface has been reached, and lowering of the pipetter and suction are stopped so that the distal end of the pipette tip is positioned within a predetermined distance from the liquid surface.(d) Next, the pipetter is lowered to further move the distal end of the pipette tip downward (within the range of a prescribed distance), and the accommodated liquid is suctioned from the container into the pipette tip while suctioning the liquid at a volume flow rate that corresponds to the suction pressure (with a controlled suction quantity),(e) changes in the suction pressure are monitored while monitoring this liquid,(f) the measured pressure change is compared with a pre-decided normal suction pressure scheme, and(g) in the case where the pressure value deviates from the normal suction pressure scheme, it is determined that the liquid is heterogeneous or the suction quantity is out of the prescribed quantity.    Patent Document 1: Japanese Unexamined Patent Publication No. 62-64912    Patent Document 2: Japanese Patent Publication No. 3065100